# NTSB MIA89LA081: Bell TH-1L, N204AP, Greenville, FL, February 8, 1989

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: February 8, 1989, 11:25 local (16:25 UTC)
- Place: Greenville, FL
- Location: 30.4668° N, 83.6353° W: Placed by OpenAirDocs: center of Greenville, FL, within about 6 miles (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=30.4668&lon=-83.6353&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report January 31, 1991
- Report: Approved by Office Director
- NTSB case key (mKey): 32395
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA89LA081
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/32395/pdf
- Page: https://openairdocs.org/ntsb/MIA89LA081

## Probable cause

INSTALLATION OF THE IMPROPER SPRAG CLUTCH ASSEMBLY BY THE OWNERS MAINTENANCE PERSONNEL RESULTING IN FAILURE OF THE SPRAG CLUTCH AND THE LOSS OF TRANSMISSION DRIVE.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, maneuvering
  - rotor drive system,clutch assembly - improper (cause)
  - maintenance,installation - improper, company maintenance personnel (cause)
  - rotor drive system,clutch assembly - failure,total (cause)
  - rotor drive system - loss,total (cause)
- Forced landing, descent - emergency
- In flight collision with object, descent - emergency
  - object - tree(s)
  - terrain condition - none suitable (contributing factor)

## Analysis

FLT EXPERIENCED LOSS OF TRANSMISSION DRIVE AND PERFORMED AN AUTOROTATION INTO TREES. EXAMINATION OF THE TRANSMISSION INDICATED THE SPRAG CLUTCH HAD FAILED AND THAT THE FAILED SPRAG CLUTCH WAS THE IMPROPER CLUTCH FOR THAT ENGINE AND TRANSMISSION. THE CLUTCH HAD BEEN INSTALLED AT TRANSMISSION OVERHAUL 140 HOURS BEFORE THE ACCIDENT.

## Aircraft

- Registration: [N204AP](https://openairdocs.org/deregistered/N204AP-2018-01-16), registration cancelled 2018-01-16, S/N 157840, built 1970 (OpenAirDocs)
- Reported make and model: BELL TH-1L
- Registry model: [Bell TH-1L](https://openairdocs.org/model/bell-th-1l) (registry code 1180817) (OpenAirDocs)
- Registry engine: [Lycoming T53-L-13](https://openairdocs.org/engine/lycoming-t53-l-13) (registry code 41551, turbo-shaft) (OpenAirDocs)
- Category: Helicopter
- Serial number: 157840
- Airframe hours: 8092
- Engines: LYCOMING T53-L-13B 1400 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Part 133
- Operator: Green Mountain Helicopter, Inc
- Registered owner: Southern Aero Corporation
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: 100 hour, January 26, 1989, 31 hours before
- Departed: GREENVILLE, FL

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 38; airline transport; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 7,853 total, 1,200 in this make and model, 7,644 as pilot in command, 32 in the last 90 days, 31 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 360° at 4 knots
- Visibility: 6 statute miles
- Lowest ceiling: none
- Temperature: 41 °F, dew point 36 °F
- Altimeter: 30.00 inHg
- Observed at: TLH, 36 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19890208031229A](https://openairdocs.org/incident/19890208031229A), Feb 8, 1989: Bell TH1L, Greenville, FL, Substantial damage. Loud noise,lost RPM. Autorotated into trees. Improper sprag clutch installed,became disengaged from stress and wear

## Other investigations on N204AP (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB LAX94LA132](https://openairdocs.org/ntsb/LAX94LA132), Feb 23, 1994: Bell TH-1L (N204AP), Etna, CA, substantial damage. Probable cause: THE FAITUGE OF THE GEAR TOOTH WHICH CAUSED THE FAILURE OF THE 42-DEGREE GEAR BOX.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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